Hello,
We had good weather Friday, so I went out to the patio to work on the problem. I dug out the pellets to get down to the auger. Thankfully, I was was right about a possible moisture issue. There was no evidence of pellets clumped together or forming a sort of cement (I had seen this years ago with an older Traeger). I was unable to twist the auger at all by hand or by pushing the "Prime" button on the controller.
I was surprised by what I found though. When I dug down to the auger I noticed that 4 or 5 pellets were jammed between the auger and the opening of the tube. I was unable to totally break these free by hand, so I broke them up with a screwdriver. They broke off and then I could advance the auger by hand. I then turned it back on and the auger started turning to load pellets into the firepot. Behaving normally.
I then cooked dinner Friday and Sunday, so it seems to be ok. I've been using pellet smokers for about 10 years, and I had never seen pellets use teamwork to prevent the auger from turning. The pellets in the hopper were made by BBQers Delight - Hickory, so it's not a case of using weird pellets.